Such devices are conventionally referred to as air brush or “spray gun”. The entrainment of the droplets of liquid is due to a low pressure generated by a Venturi effect. In principle, such a device may be used for the application of completely different types of media. To simplify matters, the following description only refers to the use of colour.
A device of the generic type is known from U.S. Pat. No. 5,454,517. A drawback of such devices is that changing the colour or cleaning the nozzle after a longer downtime period, which requires a substantial amount of time and effort whilst also involving the risk of damage to the delicate needle disposed in the nozzle, may lead to severe malfunctions or to functional failure.